SUNRPC: create stubs for xprtsock init and cleanup

Over time we will want to add some specific init and cleanup logic for the
xprtsock implementation.  Add stub routines for initialization and exit
processing.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/xprtsock.c

@@ -1502,3 +1502,21 @@ struct rpc_xprt *xs_setup_tcp(struct sockaddr *addr, size_t addrlen, struct rpc_
 
 	return xprt;
 }
+
+/**
+ * init_socket_xprt - stub
+ *
+ */
+int init_socket_xprt(void)
+{
+	return 0;
+}
+
+/**
+ * cleanup_socket_xprt - stub
+ *
+ */
+void cleanup_socket_xprt(void)
+{
+	return;
+}